Metallic sulfide flotation process



United States Patent 3,370,704 METALLIC SULFIDE FLOTATION PROCESS Robert E. Baal-son, La Grange, and Charles L. Ray, Wheaton, 111., assiguors to Armour and Company, Chicago, Ill., a corporation of Delaware No Drawing. Filed May 14, 1964, Ser. No. 367,576 15 Claims. (Cl. 209-166) This invention relates to flotation collectors for metallic sulfide ores, and more particularly relates to a new class of collectors for selectively separating copper sulfide minerals from other ore constituents, requiring in the case of oxidized copper sulfide ores no artificial sulfidization of oxidized mineral surfaces with inorganic sulfur chemicals.

An object of the present invention is to provide in the froth flotation process for the treatment of metallic sulfide ores, new and effective flotation collectors for metallic sulfide mineral recovery. A further object is to provide a method for the recovery of metallic sulfide minerals through the use of S-aliphatic isothiouronium salts as collectors. A still further object is to provide a process in which isotbiouronium halide compounds derived from fatty and aromatic halides are employed in the flotation treatment of copper sulfide ore, said isothiouronium compounds attaching to and causing flotation of copper sulfide minerals. Other specific objects and advantages will appear as the specification proceeds.

In one embodiment of the invention, S-substituted isothiouronium salts are preferably prepared by refluxing an alcoholic solution of thiourea with a fatty halide or with an aromatic halide and are represented by the following general formula:

where R is an aliphatic, cycloaliphatic, or aromatic hyrocarbon group having two or more but not more than 24 carbon atoms and preferably not more than 18 carbon atoms, or mixtures thereof, and where X is a halide such as Cl, Br, I, etc. Best results have been obtained when the hydrocarbon group has from 4 to carbon atoms. Other methods of preparation of the collectors are possible. The invention is not limited to any one method of preparation of the collectors.

The isothiouronium halide compounds thus derived are employed to condition the metallic sulfide pulp together with a frother, if desired, such as methylamyl alcohol or polypropylene glycol ether, and following the conditioning, flotation is conducted in the usual manner to effect concentration and recovery of the metallic sulfide minerals. As a specific example, copper sulfide ore is ground to a finely-divided state, and a water pulp of the fiue1y-divided ore is mixed or conditioned with about 0.03 pound of the collector and about 0.03 pound of a frother per ton of dry ore. Following conditioning, flotation is conducted for several minutes. An additional amount of collector and frother may then be added and flotation continued for another period. The flotation concentrate thus obtained may then be subjected to further upgrading operations in order to produce a concentrate of higher grade with respect to the copper minerals being recovered. The quantities of collector required may range from about 0.005 pound to about 0.5 pound per ton of dry ore treated. The required quantities depend on the nature of the ore treated and on the particular collector utilized. and do not limit the scope of the invention.

Specific examples of the collectors may be designated as benzyl-, ethyl, isopropyl-, n-butyl-, n-amyl-, isoamyl-, 2-ethylhexyl-, n-octyl-, l-methyloctyl-, dodecyl-, lauryl-, tetradecyl-, and tallow isothiouronium chloride, and other salts as defined above where the fatty halide or aromatic halide has from 2 to 24 or, preferably, from 2 to 18 carbon atoms and including mixtures of said 3,370,704 Patented Feb. 27, 1968 halides. The preferred collectors of the invention are benzylisothiouronium chloride and straight or branched carbon chain alkylisothiouronium chlorides ranging from 3 to 13 carbon atoms in the collector molecule.

Since the collectors are either water soluble or water dispersible, it is preferred to apply them to flotation as water solutions or water dispersions ranging from about 1% to about 10% active by weight.

The invention will be further illustrated by the following discussion and examples, which are illustrative of the preferred embodiments of the invention, but the invention is not limited thereby. A series of tests were conducted using several different isothiouronium collectors. The test procedure was as follows:

Example I A charge of copper ore containing about 0.70% Cu by weight was mixed with water to 50% solids and was ground to a finely-divided state in a laboratory rod mill in the presence of sufiicient calcium oxide to produce a flotation ore pulp pH of 11.0:02. The ground ore was transferred to a Denver laboratory flotation machine and diluted with water to about 20% solids. Flotation was conducted in stages by adding an isothiouronium collector to the ore pulp in increments of 0.01, 0.01, 0.02, and 0.03 pound, for a total of 0.07 pound of collector per ton of original ore. Polypropylene glycol ether frother was added to the ore pulp in amounts sufllcient to provide desirable frothing characteristics throughout each test, such amounts ranging from about 0.048 to about 0.096 pound per ton of ore. Following the addition of each increment of collector, the ore pulp was conditioned in the absence of air for 2 minutes, air was then introduced and froth flotation was conducted for 2 minutes, for a total of 8 minutes of actual flotation time. The flotation froth products were collected separately for each collector addition and analyzed for iron and copper content. For each test, the analytical results were calculated so as to show the analysis of a single, combined concentrate. The results of the various tests are shown in Table I.

TABLE I Weight Assay Percent Collector Percent Percent Recovery Floated Cu in 0oncentrate Cu Fe Ethylisotlu'ouronium chloride 3. 57 12. 23 63. 4 l3. 3 lsopropylisothiouronium chloride 6. 57 7. 71. 3 48. 9 n-filrlnylasothiouronium c on e 7. 36 7. 40 79. 0 47. 8 2-ethylhexylisothiouronium chlor1de. 6. 96 7. 33 71. 3 50. 4 n-Octyhsothiouronium chloride. 8. 00 7. 18 76. 5 53. 1 Dodecylisothiouronium chloride 6. 55 7. 24 71. 2 47. 4

The results in Table I illustrate the good grade of copper and good recovery of copper obtained in the concentrate. It is also illustrated that the number of carbon atoms and the arrangement of these carbon atoms in the hydrocarbon groups has influence on the so-called collecting power of the collector on a particular ore. For instance, the n-amyl homologue produces the highest recovery of copper from the ore tested as shown in Table I, while the ethyl and n-octyl homologues which are, respectively, shorter and longer in carbon chain length,

- produce a lower copper recovery. While many frothers may be used with the collectors of the invention with success, the preferred frothers are methylisobutyl carbinol, polypropylene glycol ether, and the polyalkoxy alkanes. Such frothers as pine oil and cresylic acid have been found mildly detrimental to the good flotation characteristics which are supplied by the collectors. It is well known to those skilled in the art that to obtain the best flotation results is often due to the selection of the best frother chemical for any given ore and collector being utilized.

In the flotation treatment of metallic sulfide ores, the pH of the ore pulp ususally has important influence on the response of the metallic sulfide minerals to flotation treatment. For instance, in the case where it is desired to float copper sulfide minerals away from iron pyrite, an ore pulp pH of from 9 to 12 or higher, depending on the particular type of collector employed, and the nature of the ore being treated, is usually maintained to prevent excessive flotation of iron sulfide. In such cases, it is desired to utilize a collector for copper sulfide minerals which of its own accord does not tend to cause excessive flotation of iron pyrite. On the other hand, it may be desired to eflect a high recovery of both copper sulfides and iron sulfides in a so-called bulk sulfide concentrate. In this case, a pH in the ore pulp must be maintained which allows flotation of iron pyrite along with the copper sulfide minerals, and a collector must be employed which provides a high recovery of both types of minerals. It will be seen in the following example that the collectors of the invention may be used under diflerent conditions of pH and may be desired increases in the flotation recovery of valuable metallic sulfide minerals. For instance, although the collectors of the invention ionize in water to produce a positively charged collector ion, they can be used to advantage with collectors that exhibit negative ionization, and both types of collectors may be present at the same time in the ore pulp. I

Example III A typical copper ore, averaging about 2.2% Cu and 9.5% Fe, was subjected to laboratory flotation treatment at a pulp pH of 11.8 to 12.0 in the presence of collectors and a polypropylene glycol ether frother. A combination of isopropylethylthionocarbamate and sodium isopropyl xanthate, which were standards for the ore being tested, were used as collectors in several flotation tests, and a combination of isopropylethylthionocarbamate and n-amylisothiouronium chloride were used as collectors in other flotation tests on the same ore, and n-amylisothiouronium chloride was also tested as the sole collector. Froth products and the cell underflow or tailing from the tests were assayed for iron and copper content. Typical test results are shown in Table III.

chosen according to the number and arrangement of carbons in the R group so as to provide the desired selectivity between copper sulfide minerals and iron pyrite.

Example II A typical copper ore averaging about 1.4% Cu and 6.5% Fe was ground to a finely-divided state and subjected to flotation treatment in a laboratory flotation cell in the usual manner by conditioning the ore pulp for 1 minute in the presence of 0.035 pound of collector and 0.038 pound of polypropylene glycol ether frother per ton of ore. Following conditioning, flotation was conducted for 9 minutes. All reagent amounts and conditions of flotation were held constant except for the pH of the ore pulp during flotation and the type of isothiouronium chloride collector employed. The froth product and the cell underflow or tailing were assayed separately for iron and copper content. The test results are shown 1n Table II.

TABLE II Isothiouronium Percent Percent Percent Chloride Pulp Concentrate Tailing Recovery Collector pH Cu Fe Cu Fe Cu Fe It is shown in Table II that the adjustment of the pH of the ore pulp has a desired eflect on the collection of iron pyrite by the collectors. It is also demonstrated that selection of an isothiouronium collector of proper carbon chain length will permit strong or weak collection of iron pyrite as desired. Since benzylisothiouronium chloride operates effectively at a lower pH range, there is a desirable rejection of iron pyrite.

It is also possible to use the collectors of the invention in combination with known collectors to bring about It can now be seen that the combination of n-amylisothiouronium chloride and isopropylethylthionocarbarnate provides better results (higher Cu recovery and lower Fe recovery) than either the standard collector combination or n-amylisothiouronium chloride alone.

It is to be understood that the isothiouronium collec tors may be used in combination with alkyl or aryl dithiophosphates, dithiocarbonates (Xanthates), dithiocarbamates, thionocarbamates, thioureas, xanthogen formates, and all such products as are commonly used for flotation treatment of metallic sulfide ores and which are usually referred to as sulfhydryl type collectors.

It is a feature of the collectors of the invention that they do not require long periods of contact with the ore pulp in order to bring about desired flotation of metallic sulfides. It is common practice with some of the so-called sulfhydryl-type collectors to add the collector to the grinding circuit before flotation and to use extended flotation times for the distinct purpose of affording a long period of contact time between collector and ore. As stated before, such long periods of contact are not necessary with the isothiouronium collectors. It is thus preferred that the isothiouronium collectors be added to the ore pulp after grinding and during or immediately before the ore pulp is subjected to agitation and aeration in flotation cell. In fact, excessive conditioning time between the isothiouronium collectors and the ore pulp beyond that necessary for flotation of all the copper sulfide minerals which can float at a given pH of the ore pulp and at a given concentration of collector in the ore pulp, serves no purpose for good recovery of the copper sulfide minerals.

Example IV A copper ore averaging 0.45% Cu and 2.31% Fe was ground for 3 minutes to a finely-divided state in a laboratory rod mill and subjected to flotation in the usual manner in a laboratory flotation machine. In each test, flotation was conducted for 2 minutes in each of two stages by adding 0.03 pound of n-amylisothiouronium collector to the flotation cell in each stage. In the first stage, 0048 pound of polypropyleneglycol ether frother was added to the ore pulp, and in the second stage 0.024 pound of polypropyleneglycol ether frother was added to: the ore pulp.

The pH of the ore pulp during flotation was 11.1 to 11.2. All test conditions were held constant except for the time of conditioning proceeding aeration of the pulp, which varied from a total of from 2 to 20 minutes, The results 6 After 4 minutes flotation, an additional 0.04 lb./t. pine oil was added to the cell and flotation conducted 5 minutes more. Froth products obtained were combined for analyses.

of testing are recorded in Table IV. 5 Reagent addition for T est 6 .--Laurylisothiouronium TAB LE 1V Total Total Total Percent Percent Percent Conditioning Flotation Contact Concentrate Tailing Recovery Time, Time, Time, minutes minutes minutes Cu Fe Cu Fe Cu Fe The results in Table IV show, for instance, that the combined conditioning time and flotation time need not exceed the relatively short period of about 8 minutes for optimum recovery of copper.

The isothiouronium salts are outstanding collectors; not only are they selective copper sulfide collectors in general, but they show evidence of being effective for oxidized copper sulfide ore. A sample of copper sulfide ore averaging about 4.0 to 4.5% Cu by weight was tested while fresh, and again after storage in a finely-divided state for one year and again after two years. The following Example V, Example VI and Example VII are illustrative.

Example V A fresh 500 gram sample of minus 10 mesh copper ore averaging 4.0 to 4.5% Cu was ground in a laboratory ball mill at 60% solids to obtain the following size distribution:

TABLE V.SCREEN ANALYSIS-BALL MILL GRIND Lime was added to the ball mill to produce a flotation pH of 12.0. The ground ore was transferred to a Fagergren laboratory flotation cell without desliming. The pulp was conditioned for one minute with 0.03 lb./t. of the collector as noted in Table VI, along with 0.027 lb./t. of a frother composed of a 1:1 mixture of methyl amyl alcohol and pine oil. Following conditioning, flotation was conducted for 4 minutes, At the end of 4 minutes, an additional 0.02 lb./t. of the collector and 0.027 lb./t. of frother was added to the cell, conditioned for 1 minute, and flotation was conducted for an additional 5 minutes. Froth products were combined for analysis. Table VI shows the metallurgical results obtained with several isothiouronium chloride salts.

Example VI .Oxidized copper are A 500 gram sample of the same ore sample described in Example V was, after storage for about 1 year, subjected to the same general test procedure as described in Example V except for the following:

Reagent addition for Test 5.Octylisothiouronium chloride was added to the cell at 0.05 lb./ t. along with 0.08 lb./t. of pine oil as frother and conditioned 1 minute.

TABLE VII Chain Length Analyses, Percent Cu RecoveryPercent Test of Isothiouro- Distribution of N o. nium Chloride Concentrate Tails Cu in Concentrate 5 8 carbon- 20. 51 0. 45 89.8 6 12 carbon. 19. 55 0. 55 87. 2

Example VIl.Oxidize'd copper are A 500 gram sample of the same ore sample described in Example V was, after storage for about 2 years, subjected to the same general test procedure as described in Example VI. The two year storage period provided ample opportunity for severe oxidation of mineral surfaces. In each test, the collector was added to the cell at 0.05 lb./t. along with 0.12 lb./t. of a frother composed of a 1:1 mixture of pine oil and isopropanol. Following conditioning and flotation for 4 minutes, an additional 0.08 lb./t. of the frother was added and flotation was continued for 5 minutes more. Table VIII shows metallurgical results obtained using octylisothiouronium chloride and a dixanthogen-type collector as a standard in separate tests.

Example VIII A charge of copper ore containing about 0.45% Cu by weight was mixed with water to 50% solids, and the process carried out as described in Example I except that dodecylisothiouronium bromide was used in one test and n-amylisothiouronium chloride was used in a com panion test, the results being shown in Table 1X.

TABLE IX Wt. Assay Percent Recovery Collector Percent Percent Cu Floated in Concen. Cu Fe Dodecylisothiouronium bromide 5. 68 6. 31 84. 2 49. 9 n-Arnylisothoiuronium c r' e 6. 76 5. 62 83. 6 49. 5

While in the foregoing specification we have set forth specific procedure in considerable detail for the purpose of illustrating embodiments of the invention, it will be understood that such details of procedure may be varied 7 widely by those skilled in the art without departing from the spirit of our invention.

We claim:

1. In a process for the separation of metallic sulfide ores by froth flotation, the steps of conditioning a water suspension of finely-divided metallic sulfide ores selected from the group consisting of copper and iron sulfide ores with a collector comprising an S-substituted isothioronium salt having the structure [RSC(NH +X- where R is an aliphatic, cycloaliphatic or aromatic hydrocarbon having from 2 to 24 carbon atoms and where X is a halide, and separating as froth product a metallic sulfide concentrate selected from the group consisting of said copper and iron sulfide ores.

2. The process of claim 1 in which the hydrocarbon component has from 2 to 18 carbon atoms.

3. The process of claim 1 in which the hydrocarbon component has from 4 to carbon atoms.

4. The process of claim 1 in which the halide is chloride.

5. In a process for the separation of metallic sulfide ores by froth flotation, the step of conditioning a water suspension of finely-divided metallic sulfide ores selected from the group consisting of copper and iron sulfide ores with a collector selected from the group consisting of straight and branched carbon chain alkylisothiouronium chlorides having from 3 to 13 carbon atoms in the collector molecule, and separating as froth product a sulfide concentrate selected from the group consisting of copper and iron sulfide ores.

6. A process according to claim 1 in which the conditioning collector is benzylisothiouronium chloride.

7. A process according to claim 1 in which the conditioning collector is n-amylisothiouronium chloride.

8. A process according to claim 1 in which the conditioning collector is tetradecylisothiouronium chloride.

9. In a process for the separation of copper sulfide ores by froth flotation, the step of conditioning a water suspension of finely-divided coppersulfide ore with a-collector consisting of S-aliphatic isothiouronium salt having the structure [RSC(NH ]+X where R is an aliphatic hydrocarbon having 2 to 18 carbon atoms and where X is a halide, and separating as froth float product a concentrate of copper sulfide ore.

10. The process of claim 9 in which the hydrocarbon component comprises a mixture of aliphatic hydrocarbons having from 2 to 18 carbon atoms.

11. The process of claim 9 in which the halide is chloride.

12. The process'of claim 9 in which the halide is bromide. 7

13. A process according to claim 9 in which the conditioning collector comprises n-amylisothiouronium chloride and a frothing agent.

14. A process according to claim 9 in which the conditioning collector comprises n-amylisothiouronium chloride and a frothing agent.

15. A process according to claim 1 in which the conditioning collector is n-butyl isothiouronium chloride.

.References Cited UNITED STATES PATENTS 1,364,307 l/l921 Perkins V 209l66 2,120,217 6/1938 Harris 209-166 2,336,868 12/1943 Jayne 209--l66 2,691,635 10/1954 Harris 252-61 X 3,093,666 6/1963 Du Brow 252-61 X HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner. 

1. IN A PROCESS FOR THE SEPARATION OF METALLIC SULFIDE ORES BY FROTH FLOTATION, THE STEPS OF CONDITIONING A WATER SUSPENSION OF FINELY-DIVIDED METALLIC SULFIDE ORES SELECTED FROM THE GROUP CONSISTING OF COPPER AND IRON SULFIDE ORES WITH A COLLECTOR COMPRISING AN S-SUBSTITUTED ISOTHIORONIUM SALT HAVING THE STRUCTURE $(RSC(NH2)2$)+X-WHERE R IS AN ALIPHATIC, CYCLOALIPHATIC OR AROMATIC HYDROCARBON HAVING FROM 2 TO 24 CARBON ATOMS AND WHERE X IS A HALIDE, AND SEPARATING AS FROTH PRODUCT A METALLIC SULFIDE CONCENTRATE SELECTED FROM THE GROUP CONSISTING OF SAID COPPER AND IRON SULFIDE ORES. 